Pneumatic power tools are commonly used in factories due to their durability and dependability. Examples of such power tools include nut runners and screw drivers used to tighten threaded fasteners.
There has long been a need for a dependable system to validate fastener tightening on pneumatic tools without adding wires to the air supply hose. One of the advantages of pneumatic tools is that they require only a simple connection to an air line to be operational. There is no need to provide electrical connections that may be interrupted if wires break or connectors become loose or corroded. If wires are inserted either inside an air supply hose or are attached to the outside of the air supply hose, the simplicity of the pneumatic tool is compromised. Adding wires to an air hose reduces flexibility and increases the complexity of setting up the tool for operation.
In the prior art, electronic strain gauges have been hard-wired to either pneumatic or electric tools in an attempt to provide fastener tightening validation. Generally strain gauges are used to measure dynamic torque. Such strain gauges are calibrated in a laboratory and can provide an alarm if the strain gauge is not within preset strain measurement limits. This type of system is not easily adapted to pneumatic tools due to the above-noted problems associated with running a wire to the strain gauge. Electronically monitoring operation of a pneumatic tool compromises the objectives of simplicity and durability and unreasonably adds to the cost of such systems and the cost of tool operation.
It has been found that complicated or unreliable electronic systems added to pneumatic tools may be disconnected or overridden. For a system to be utilized it should be automatic and must not complicate or unduly interfere with use of pneumatic tools in production.
One example of a prior art system for monitoring and controlling fluid-driven tools is disclosed in U.S. Pat. No. 5,592,396. The '396 patent discloses a flow sensor that is connected by wires through a preamplifier to a data collection computer. The flow sensor or flow meter disclosed in the '396 patent is a Venturi-type differential pressure flow meter that is coupled with a semiconductor pressure sensor transducer. This system is inaccurate because it relies upon the measurement of pressure. This system also suffers from the disadvantages noted above relating to adding wires to pneumatic tools.
These and other problems encountered by prior art monitoring systems for pneumatic tools are addressed by the wireless monitoring system for pneumatic tools of the present invention.